The faces behind famous voices – Tom Kenny, another veteran voice actor, hit the big time in 1999 with the role of "SpongeBob Squarepants," which remains one of the most popular cable series of all time. The Nickelodeon cartoon is still going strong.

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The faces behind famous voices – H. Jon Benjamin has one of the most distinctive voices, going back to the low-budget series, "Home Movies." He has gone on to bigger things as the title characters in two critically-acclaimed shows, "Bob's Burgers" and "Archer."

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The faces behind famous voices – Rob Paulsen has been not one, but two "Teenage Mutant Ninja Turtles." In the 1980s, he was Raphael, and he's now playing Donatello on the Nickelodeon series. He was also two of the main characters on that 1990s favorite, "Animaniacs." He played Pinky, also on the show "Pinky and the Brain," and Wakko Warner -- just ask him to sing the "Geography Song."

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The faces behind famous voices – These guys are responsible for some of the most enduring animated characters on television today. From Fox to Comedy Central, "Futurama" - now in its final season - has kept audiences rolling. Meet, from left to right, Maurice LaMarche (Kif Kroker), Billy West (Fry, Professor Farnsworth, Dr. Zoidberg), and John DiMaggio (Bender).

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The faces behind famous voices – Yuri Lowenthal, a veteran on English dubbing work for Japanese anime, is perhaps best known as "Ben 10." He also bears a striking resemblance to the popular Cartoon Network character. (Cartoon Network is a Time Warner company, as is CNN.)

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The faces behind famous voices – Larry Kenney is the booming voice who got kids' imaginations going by exclaiming, "Thundercats, ho!" Yes, he was Lion-O on the original 1980s "Thundercats."

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The faces behind famous voices – Nancy Cartwright has spent well over two decades as a 10-year-old boy. She is the voice that launched oodles of merchandise as Bart Simpson of the long-running "Simpsons."

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The faces behind famous voices – Jim Cummings has been a denizen of the Hundred Acre Woods for almost a quarter century. He is the third actor to portray Winnie the Pooh in the various Disney films and cartoon series, following Sterling Holloway and Hal Smith. He is also the current voice of Tigger. On the Warner Bros. side of things, he has played the Tasmanian Devil for many years 1990s cartoon fans will remember him as Darkwing Duck.

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The faces behind famous voices – Cree Summer may be recognizable for her role as Freddie on "A Different World," but her voice was already famous. She played Penny, the niece of "Inspector Gadget" as a teenager. Her unique voice could also be heard as Elmyra on "Tiny Toon Adventures."

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The faces behind famous voices – Optimus Prime and Megatron, the yin and yang of the "Transformers" franchise, have sold millions of toys for nearly 30 years, not to mention those blockbuster movies. Peter Cullen, left, has been the instantly recognizable voice of Optimus for almost all of those years. Frank Welker -- a veteran of hundreds of voice roles -- recently returned to the part of Megatron on the animated series, "Transformers Prime," co-starring with his old friend Cullen.

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The faces behind famous voices – Paige O'Hara and Robbie Benson led the cast of the first animated film ever nominated for Best Picture, "Beauty and the Beast." They have returned to their roles as Belle and the Beast in various Disney productions many times since.

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Story highlights

You may not recognize their faces, but some voice actors are working steadily

One of the most famous, Seth MacFarlane recently hosted "Saturday Night Live"

Actors say the Internet has helped to grow their fan base

Frank Welker's name may not immediately ring a bell to you, but you almost certainly know his voice. He's acted in nearly 700 films and television shows.

From Fred in "Scooby Doo" to Ray in "The Real Ghostbusters" to the most recent "Garfield" -- if it's an animated show, there's a very good chance you'll hear Welker's work (he also specializes in animals, like "Aladdin's" Abu).

He can currently be heard reprising his memorable role as the evil Megatron on "Transformers Prime," with his old friend, Peter Cullen, who plays one of the most noble characters ever created, Optimus Prime. Cullen was also a mainstay of 1980s animation, in roles such as Venger in "Dungeons & Dragons."

Welker and Cullen make their living as voice actors and it's not easy to forget, as the pair of them often break into voices like John Wayne, Peter Lorre and Jabberjaw, one of Welker's favorites.

However, more and more A-list actors are joining the voice-over club over the last 20 years.

It's even gotten to the point where Chris Rock, star of the "Madagascar" franchise, took the opportunity of presenting an animation Oscar to quip about how "easy" it is to do voice work.

Rock joked that all he had to do was say the lines, "And then they give me a million dollars." (No less than Danny DeVito took issue with that characterization.)

Voice actor Seth MacFarlane -- creator of "Family Guy," "American Dad" and "The Cleveland Show" -- is enough of an A-lister to host both "Saturday Night Live" and next year's Oscars.

So how has the world of voice acting changed since Welker and Cullen's early days (besides the fact that a show like "Mighty Man and Yukk," their first job together, probably wouldn't get made today)?

"The technology has changed a lot," Welker told CNN.

"You see the CGI animation is so pretty and you could do a lot more with it than our old flat animation which I still like, of course. Watching those shows absolutely blows me away on an HD screen. You see so much more detail. It gives the actor more opportunity to bend your voice and be more subtle."

Cullen said, "The respect level (for voice acting) is climbing and climbing faster than it ever did before in the last few years. The studios are recognizing they don't have to hire a big name actor. People don't know the difference in most cases. They're finding they can take a chance with talent and accomplish the same thing."

Welker also noted that the Internet has made a big difference, and made it easier for fans to follow particular voice actors.

"In the old days doing the show, we never got one piece of fan mail," he said. "We had no idea there was an audience out there. The only way to tell there was some interest was if we got picked up for another season -- oh, somebody liked us."

Crispin Freeman became a voice actor in 1997, just at the time when animation attracting A-listers was going strong. He's best known for his work dubbing Japanese anime like "Howl's Moving Castle" and most recently Cartoon Network's "Young Justice." Cartoon Network is owned CNN's parent company.

"Voice actors have always been quite popular in Japan, but American culture is now becoming more aware of the artistic contribution of voice actors because of the swell in popularity of video games and animated films," he said.

"Not only have both mediums been expanding their market penetration in America in recent years, but the maturity of the storytelling in each medium has grown as well," Freeman said.

"This attracts an older audience that is more curious about the performers behind their favorite animation or video game character. It seems that as we see a convergence of film, animation and video games, American audiences will become more and more aware of the importance of voice acting."

Patrick Seitz has a slightly different perspective. He got into voicing even more recently, in 2000, and is mostly involved with the world of video game voice work, as well as anime.

"I don't know if voice acting is more respected, per se, but I do think it's a higher profile pursuit than it was in decades past," he said.

"Games progressing to the point where they can be fully voiced has opened a whole new sphere of awareness and fandom, and ever since the animated feature films got the idea to fill their casts with celebrities (for better or for worse), they've never looked back."

But he certainly agrees with Cullen and Welker that online fandom for voice actors has been a game changer.

"It's amazing how completely some of the fans have sussed out our vocal fingerprint, so to speak. I've had folks identify me based on nothing more than a roar."